Police Concealed Use of a Device That Can Follow Suspected Criminals

At the insistence of federal law enforcement officials, Florida police concealed their use of a device that can track suspected criminals' cellphones, according to emails obtained by the American Civil Liberties Union.

The 2009 email chain, which the civil rights group received in response to a public-records request, sheds light on the government's efforts to keep the details of a surveillance tool known as a "stingray" out...